The state of the art includes electric arc furnaces (EAF) in which each electrode or cathode made of graphite is vertically supported by a clamp located at the end of a horizontal arm which has the other end connected to a bearing column.
The graphite column which constitutes the electrode is obtained by connecting several segments together, joined by means of intermediate elements called nipples, made of the same material.
The maximum thermo-mechanical tensions and the dynamic forces due to the vibration of the arm occur both in correspondence with the intermediate joining elements and in correspondence with the clamp of the electrode-bearing arm.
These stresses can cause the electrode to break: the greater the free length of inflection (height) of the column and the cantilever of the arm, and the higher the temperature of the electrode, the greater the probability of the electrode breaking.
In the electric furnace, in fact, during the step when the metal is melting, the graphite column normally reaches very high temperatures due to the effect of the electric arc, the passage of the electric currents employed (Joule effect) and the heat exchange with the inner environment of the furnace, and therefore it tends to be progressively consumed. It is thus necessary to replace it with new segments of graphite.
The state of the art includes cooling systems and devices which act prevalently, if not exclusively, in correspondence with the metallic portion of the electrode, to remove a part of the heat which migrates through conduction from the graphite column towards the metallic part. In this way these systems attempt to lower the temperature of the graphite column by lowering the temperature of the metallic part of the electrode.
Such cooling systems and devices however are not completely satisfactory and never achieve their set purpose; hence, in practice, they do not perform an efficient cooling of the lower part, made of graphite, of the cathode.
The present Applicant has devised, tested and embodied this invention to overcome the shortcomings of the state of the art and to obtain further advantages.